It was hypothesized that grazing management could mitigate grasshopper outbreaks on native rangeland in the northern Great Plains. Key practices would require deliberate variation in timing and intensity of grazing events, preservation of canopy during critical periods of grasshopper development, and reductions in areas of bare soil. The twice-over rotational grazing system appeared compatible with those requirements.Grasshopper population trends were monitored during 1993-1995 and 1997-1998 on commercial native rangeland under twice-over rotational grazing vs traditional season-long grazing. A ubiquitous pest grasshopper, Melanoplus sanguinipes (Fabricius), occurred at every sample site during each year in numbers sufficient to provide life history parameters for comparison between treatments. Under rotational grazing, the nymphs developed significantly slower and their stage-specific survival rates were significantly lower and less variable. Consequently, significantly fewer adults were produced significantly later in the season under rotational grazing.Seasonal presence of all grasshopper species combined averaged 3.3X higher under season-long grazing than under rotational grazing. Local outbreaks that generated 18 and 27 adult grasshoppers per m 2 under season-long grazing in 1997 and 1998, respectively, did not occur under rotational grazing. The outbreaks consumed 91% and 168%, respectively, as much forage as had been allocated for livestock, as opposed to 10% and 23%, respectively, under rotational grazing.Of 9 important grasshopper species, none were significantly more abundant at rotational sites than at season-long sites. Three species that were primary contributors to outbreaks under season-long grazing remained innocuous under rotational grazing. It therefore appears that outbreak suppression through grazing management is feasible in the northern Great Plains.In a study of statistical density dependence among rangeland grasshoppers in Montana, Kemp and Dennis (1993) reported equilibrium or "return tendency" parameters for populations in 3 regions of the state; northern plains, southern plains, and western mountains. 5.4, ) and mean (6.1, 6.2, 6.3 m -2 ) densities of adult grasshoppers were similar for the respective regions. However, estimated regional carrying capacities were much higher for the 2 plains regions than for the mountains (8.9 and 8.6 vs 6.3 m -2 , respectively). Consequently, grasshopper populations were much more variable in the plains, and grossly over-shot the carrying capacity (i.e., reached outbreak levels) much more frequently than in the mountains. These results provided useful insights for assessing opportunities for
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